Browsing by Author "Pai, Yung-Min"

Now showing 1 - 9 of 9

A Light Guide Plate That Uses Asymmetric Intensity Distribution of Mini-LEDs for the Planar Illuminator
(2019-03-08)
Ye, Zhi-Ting
;
Pai, Yung-Min
;
Chen, Cheng-Huan
;
Kuo, Hao-Chung
;
Chen, Lung-Chien
Traditional backlights are designed with new dot patterns, and then injection molding, laser beam fabrication, or UV (Ultraviolet) roll-to-plate imprinting is used to apply dot patterns to a light guide plate-the process consumes considerable time and resources. Therefore, we propose a novel light guide design that does not use a dot pattern. We designed an asymmetric intensity distribution of mini-LEDs (Light Emitting Diode) and a light guide plate with a fully printed diffusion reflection on the bottom surface for a planar illuminator. The design rules for the proposed architecture are described in this paper. The archetype design with a 152.4 mm circular down-light has a diameter of 143 mm for the planar light source module. The experiment achieved a total efficiency of 85% and uniformity of 92.6%.
Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall
(2018-11-01)
Pai, Yung-Min
;
Lin, Chih-Hao
;
Lee, Chun-Fu
;
Lin, Chun-Peng
;
Chen, Cheng-Huan
To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output could be enhanced 18.38% of DUV-LEDs packaged with the aluminum-based sidewall.
Hybrid-type white LEDs based on inorganic halide perovskite QDs: candidates for wide color gamut display backlights
(2019-05-01)
Lin, Chih-Hao
;
Verma, Akta
;
Kang, Chieh-Yu
;
Pai, Yung-Min
;
Chen, Tzu-Yu
We demonstrate inorganic halide perovskite quantum-dots-based white light-emitting diodes via three different geometries, including liquid, solid, and hybrid types. Problems of fast anion exchange and aggregation in the cases of liquid- and solid-type devices are discussed in detail and push us to move towards the fabrication of a hybrid-type device structure. The experiment results illustrate that a hybrid-type device has the highest luminance efficiency (51 lm/W) and a wide color gamut (122% of NTSC and 91% of Rec. 2020). Therefore, we conclude that a hybrid-type device can provide an outstanding color gamut for high color gamut display applications. (c) 2019 Chinese Laser Press
Liquid Type Nontoxic Photoluminescent Nanomaterials for High Color Quality White-Light-Emitting Diode
(2018-12-22)
Lin, Chih-Hao
;
Pai, Yung-Min
;
Lee, Chun-Fu
;
Verma, Akta
;
Lin, Huang-Yu
High-brightness white-light-emitting diodes (w-LEDs) with excellent color quality is demonstrated by using nontoxic nanomaterials. Previously, we have reported the high color quality w-LEDs with heavy-metal phosphor and quantum dots (QDs), which may cause environmental hazards. In the present work, liquid-type white LEDs composed of nontoxic materials, named as graphene and porous silicon quantum dots are fabricated with a high color rendering index (CRI) value gain up to 95. The liquid-typed device structure possesses minimized surface temperature and 25% higher value of luminous efficiency as compare to dispensing-typed structure. Further, the as-prepared device is environment friendly and attributed to low toxicity. The low toxicity and high R9 (87) component values were conjectured to produce new or improve current methods toward bioimaging application.
Nanoparticle-Doped Polydimethylsiloxane Fluid Enhances the Optical Performance of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
(2019-07-15)
Ye, Zhi Ting
;
Pai, Yung-Min
;
Lin, Chih-Hao
;
Chen, Lung-Chien
;
Hong Thai Nguyen
This paper proposes a new encapsulation structure for aluminum nitride-based deep UV light-emitting diodes (DUV-LEDs) and eutectic flip chips containing polydimethylsiloxane (PDMS) fluid doped with SiO2 nanoparticles (NPs) with a UV-transparent quartz hemispherical glass cover. Experimental results reveal that the proposed encapsulation structure has considerably higher light output power than the traditional one. The light extraction efficiency was increased by 66.49% when the forward current of the DUV-LED was 200mA. Doping the PDMS fluid with SiO2 NPs resulted in higher light output power than that of undoped fluid. The maximum efficiency was achieved at a doping concentration of 0.2wt%. The optical output power at 200mA forward current of the encapsulation structure with NP doping of the fluid was 15% higher than that without NP doping. The optical output power of the proposed encapsulation structure was 81.49% higher than that of the traditional encapsulation structure. The enhanced light output power was due to light scattering caused by the SiO2 NPs and the increased average refractive index. The encapsulation temperature can be reduced by 4 degrees C at a driving current of 200mA by using the proposed encapsulation structure.
Novel Method for Estimating Phosphor Conversion Efficiency of Light-Emitting Diodes
(2018-12-01)
Lin, Chih-Hao
;
Huang, Che-Hsuan
;
Pai, Yung-Min
;
Lee, Chung-Fu
;
Lin, Chien-Chung
This study presents a novel method for estimating the phosphor conversion efficiency of white light-emitting diodes (WLEDs) with different ratios of phosphors. Numerous attempts have been made for predicting the phosphor conversion efficiency of WLEDs using Monte Carlo ray tracing and the Mie scattering theory. However, because efficiency depends on the phosphor concentration, obtaining a tight match between this model and the experimental results remains a major challenge. An accurate prediction depends on various parameters, including particle size, morphology, and packaging process criteria. Therefore, we developed an efficient model that can successfully correlate the total absorption ratio to the phosphor concentration using a simple equation for estimating the spectra and lumen output. The novel and efficient method proposed here can accelerate WLED development by reducing costs and saving fabrication time.
Optimization of nano-honeycomb structures for flexible w-LEDs
(2017-08-21)
Lin, Huang-Yu
;
Pai, Yung-Min
;
Shi, Jing-xing
;
Chen, Xin-Yin
;
Lin, Chung-Hsiang
This study presents the low cost fabrication of flexible white-light-emitting diodes (w-LEDs) with nano-honeycomb-structured phosphor films. Extending the dimensions of the nano-honeycomb structures improved the color uniformity of the flexible samples, and the 950-nm pattern sample demonstrated optimal color uniformity because this nano-pattern exhibited an excellent diffusion ability owing to its pitch size. In addition to color uniformity, the use of this nano-pattern improved the luminous efficiency. The 750-nm pattern exhibited the highest luminous efficiency (235.8 lm/W), which was approximately 7% higher than that exhibited by a non-patterned phosphor film sample. Thus, flexible w-LEDs with nano-honeycomb structure optimization have great potential to be used as next-generation lighting sources. (C) 2017 Optical Society of America
Square Column Structure of High Efficiency, Reliable, Uniformly Flexible LED Devices
(2018-12-01)
Lin, Chih-Hao
;
Pai, Yung-Min
;
Kang, Chieh-Yu
;
Lin, Huang-Yu
;
Lee, Chun-Fu
This study demonstrates that flexible white LEDs, doped with diffusion particles and with a square column structure, have excellent luminosity, uniformity, and bending reliability. This large area (5 cm x 5 cm) square column flexible device had a smaller thickness (2 mm), and enhancements in both luminous efficiency (29.5%) and uniformity (44.6%) compared to the characteristics of the 6 mm reference sample. Optimization of the reflective layer coating for the square column, flexible white LED was achieved with a higher luminous efficiency (171 lm/w) and uniformity (92%). We designed a novel lightning bolt electrode to improve reliability and bendability. After the bending test, the blue flexible LED had a lower bending diameter (10 mm) but more bending circles (increased to 2000 times.
Ultrawide Color Gamut Perovskite and CdSe/ZnS Quantum-Dots-Based White Light-Emitting Diode with High Luminous Efficiency
(2019-09-01)
Lin, Chih-Hao
;
Kang, Chieh-Yu
;
Verma, Akta
;
Wu, Tingzhu
;
Pai, Yung-Min
We demonstrate excellent color quality of liquid-type white light-emitting diodes (WLEDs) using a combination of green light-emitting CsPbBr3 and red light-emitting CdSe/ZnS quantum dots (QDs). Previously, we reported red (CsPbBr1.2I1.8) and green (CsPbBr3) perovskite QDs (PQDs)-based WLEDs with high color gamut, which manifested fast anion exchange and stability issues. Herein, the replacement of red PQDs with CdSe/ZnS QDs has resolved the aforementioned problems effectively and improved both stability and efficiency. Further, the proposed liquid-type device possesses outstanding color gamut performance (132% of National Television System Committee and 99% of Rec. 2020). It also shows a high efficiency of 66 lm/W and an excellent long-term operation stability for over 1000 h.